1. Technical Field
The subject matter described herein relates to a modem architecture that supports joint source channel decoding (JSCD).
2. Description of Related Art
Various communication standards exist for enabling wireless voice calls and high-speed data communications using mobile devices. For instance, Long Term Evolution (LTE) is a standard for wireless data communications, and is an evolution of the Universal Mobile Telecommunications System (UTMS) and Global System for Mobile Communications (GSM) standards. LTE is referred as a fourth generation (4G) mobile communication standard, and is a successor to third generation (3G) (e.g., UTMS) and second generation (2G) (e.g., GSM) mobile communication standards. In legacy 2G and 3G mobile telecommunications systems, voice calls are circuit-switched. In contrast, LTE enables voice calls to be made in a packet-switched manner over IP (Internet protocol), which is referred to as “VoLTE” (voice over LTE), and is supported by the IP Multimedia Subsystem (IMS). Thus, as LTE becomes more widespread, communication devices and voice call networks will need to be reengineered to handle the VoLTE voice calls.
Communication systems that implement one or more of these communication standards to exchange data may encode the data at a transmitting end and decode the data at a receiving end. An encoder may be used to encode the data, and a decoder may be used to decode the data. Implementations of encoder/decoder pairs can be used in a wide range of communication systems and devices, such as mobile devices, desktop computers and servers, computer networks, telecommunication networks, and the like. The encoding and decoding of the transmitted data may allow for increased data integrity, security of the data, compression of the data, etc.
When decoding data that was received over a communication channel, a decoder may attempt to model the received data in order to determine if errors exist. Different types of decoders may model data in different ways based on how the data was encoded. For example, a turbo decoder is a type of decoder that may be used in a device to decode received data and model the data to determine errors. A turbo decoder may include a pair of sub-decoders that work cooperatively to refine and improve the estimate of the original information bits received in a data packet.
LTE has several built-in mechanisms that may be leveraged by decoders to improve performance in adverse channel conditions, including retransmissions, code rate adjustments, and modulation scheme alterations. For instance, improved performance can be obtained by using an increased number of retransmissions, a lower coding rate to provide more redundancy, and/or a modulation scheme that sends fewer bits per symbol. However, using any of these mechanisms can have undesired affects, such as increasing power usage in a user device, decreasing network capacity, lowering spectral efficiency, and/or other disadvantage(s). As such, merely using these mechanisms that are built into LTE to improve channel performance is not likely to be enough to differentiate a service provider or device manufacturer from competitors.